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School of Medicine
Zika Virus: Answers to Common Questions
With the heightened media coverage of the Zika virus, it’s only natural to feel anxious about it. But it’s important to know the facts.
What is Zika virus?
Zika is a mosquito-borne virus similar to dengue fever, yellow fever or West Nile virus. Zika infection is primarily spread by Aedes aegypti mosquitos.
What are the symptoms of Zika virus?
Symptoms of the Zika virus are generally mild and include fever, rash, joint pain and headaches. People infected with the Zika virus rarely need hospitalization. Only about one in five infected individuals will exhibit any symptoms.
How is Zika virus spread?
Zika virus is primarily spread through the bite of infected mosquitos. If a pregnant woman is bitten by an infected mosquito, the infection can cross the placenta, infecting the fetus. The virus has also been transmitted sexually and through blood transfusion or laboratory exposure. The Food and Drug Administration has published guidelines to help protect the blood supply.
How is Zika virus transmitted through sexual contact?
There is evidence that Zika virus can be sexually transmitted from a man to his sexual partners and from a female to her sexual partners, especially if they are symptomatic. If a man or woman has lived in, traveled to or plans to travel to an area affected by Zika virus and is sexually active, using condoms the right way every time he or she has sex can reduce the chance that he or she will sexually transmit Zika virus. However, abstaining from sex for eight weeks after traveling to an affected region if you are a female and six months if you are a male is the best way to ensure transmission does not occur. If a woman who is pregnant or trying to conceive is concerned that her male partner may have had or has Zika, she should talk to her health care provider about her male sex partner’s travel history, including how long he stayed, whether he took steps to prevent getting mosquito bites and if she had sex without a condom since his return.
Why are pregnant women particularly affected by Zika virus?
Zika during pregnancy can cause microcephaly and other neurologic abnormalities. For more information on how the Zika virus affects pregnant women, read a Zika virus Q&A from maternal-fetal medicine expert Dr. Jeanne Sheffield.
Can a previous Zika infection cause a woman who later gets pregnant to have a baby with microcephaly?
There is currently no evidence to suggest that Zika virus presents a risk of birth defects for future pregnancies after it has cleared from the bloodstream. Zika virus usually remains in the blood of an infected person for about a week but may be present longer in semen and urine.
How is Zika diagnosed?
Zika virus is diagnosed by a blood test. If you are experiencing fever, rash, joint pain and red eyes, especially after recent travel to an affected country or being bitten by a mosquito, please visit your health care provider, who can determine if a blood test is needed. Urine may also be collected if you have recently had or currently have symptoms.
Is there a vaccine or treatment for Zika virus?
Vaccines and treatment are being investigated, but there currently is no medication available to prevent or treat Zika infection. If you exhibit symptoms, these can be treated with plenty of rest, fluids to prevent dehydration and acetaminophen for fever. If you are pregnant, you will continue to undergo regular monitoring to watch for fetal abnormalities after the symptoms have passed.
How do I protect myself?
The best way to protect yourself is to limit your exposure by not traveling to countries affected by Zika outbreaks. When traveling to an affected area, wear long-sleeve shirts and long pants to limit skin exposure, stay indoors in screened-in and/or air-conditioned rooms as much as possible, and use mosquito netting. Pregnant women can safely use Environmental Protection Agency-approved bug spray with DEET or picardin or permethrin-infused clothing. Women who recently traveled to an area affected by Zika virus and who exhibit symptoms should wait eight weeks before trying to get pregnant. Men who have symptoms after traveling to affected areas should wait six months before conceiving.
Is there concern that Zika will spread throughout the United States?
The continental United States does have the strains of mosquitoes that can become infected with and spread Zika virus, including Aedes aegypti. Please click here to find a map of the approximate distribution of Aedes mosquitos in the U.S. from the Centers for Disease Control and Prevention. Cases of Zika in Florida and Texas have been reported as documented cases of local transmission within the continental U.S. Johns Hopkins experts believe that mosquito control efforts and the widespread use of air conditioning in this country will help to slow the spread of Zika to the continental U.S., but residents should take all recommended measures to prevent mosquito bites.
About Travel Recommendations
What are the current recommendations regarding travel to Zika-affected areas?
The Centers for Disease Control and Prevention keeps an updated list of areas where Zika outbreaks have occurred. For anyone traveling to these locations, avoiding mosquito bites is the best way to avoid exposure to the Zika virus. Pregnant women should speak to their obstetrician-gynecologist if they must travel to an affected area, as well as take precautions to prevent mosquito bites. For pregnant women who have traveled to Zika-affected countries, your physician will perform a test for evidence of Zika virus infection. You will also have at least one ultrasound to evaluate your fetus for infection. If a man or woman travels to an area of active Zika virus infection and has a pregnant partner, they should abstain from sexual activity or consistently and correctly use condoms during sex for the duration of the pregnancy.
About Potential Mosquito Carriers
Which mosquitoes can carry Zika virus?
Zika virus is carried primarily by Aedes species mosquitos, specifically, Aedes aegypti and Aedes albopictus.
Where do mosquitoes that can carry Zika virus live?
The mosquitoes that can carry Zika virus tend to live in warmer environments, including tropical, subtropical and, in some cases, temperate climates. The Aedes aegypti and Aedes albopictus mosquitoes can be found in the U.S. The Centers for Disease Control and Prevention (CDC) has a map of the estimated range of these mosquitoes in the U.S. Visit the CDC’s website to also view a map of countries and territories with active Zika virus transmission.
How does a mosquito transmit Zika virus?
Mosquitoes become infected when they bite a person actively infected with the virus and take in virus-containing blood. They then spread the virus to other people through subsequent bites. Only female mosquitoes bite people; they need blood to lay eggs. In a female mosquito, the virus travels from the gut to the salivary glands and is injected into the next human victim.
What can I do to prevent mosquitoes from breeding?
To prevent mosquitoes from breeding near your home, consider the following prevention methods:
- Once a week, empty and scrub, cover, or throw out any items outside that hold water, like tires, buckets, planters, toys, pool covers, birdbaths, flowerpots or trash containers.
- Tightly cover water storage containers (i.e., buckets, rain barrels, etc.).
- For water storage containers without lids, use wire mesh with holes smaller than an adult mosquito.
- Use larvicides to treat large containers of water that will not be used for drinking and cannot be covered or dumped out.
- Use an outdoor flying insect spray in dark, humid areas where mosquitoes rest, like under patio furniture, or in the carport or garage. When using insecticides, always follow label instructions.
- If you have a septic tank, repair cracks or gaps. Cover open vent or plumbing pipes using wire mesh with holes smaller than an adult mosquito.
What should I do if I’m bitten by a mosquito?
If you notice a mosquito bite, you can use over-the-counter cortisone or antihistamine creams. You should generally avoid scratching the bite, as it can tear the skin and, in rare cases, lead to an infection.
Pregnant women who have traveled to an area with active Zika transmission should consult with their Ob/Gyn upon their return and before using medications.